The PrismWirelessChipset made by Intersil is one of the most common 802.11b WirelessChipsets available today. It is also one of the most feature complete in terms of what the drivers will allow you to do with it.
There are several versions of the Prism chipset around, I'm not entirely sure what the differences between them are. I believe Prism1 chipsets are extinct and you are unlikely to find them anymore. Prism2/2.5 chipsets support 802.11b and are the most commonly found. Prism3 is starting to become more widely used, and supports 802.11g as well as 802.11b.
Prism Chipsets have great linux support any of the following drivers will work
The Prism3-based cards use the kernel's prism54 driver.
This CardBus card uses a Prism2 or 2.5 chip, and only supports 802.11b and WEP. Confusingly, the iwconfig command shows Nickname: "Prism I" for this card, but it is definitely not using a prism1 chipset. It just works in Ubuntu 5.04 (Hoary), where the cardmgr automatically loads the Orinoco and orinoco_cs drivers. However, my network uses WPA, and wpasupplicant doesn't work with the orinoco driver, but it does with the HostAP driver, which doesn't come bundled with Ubuntu. It looks like Hoary doesn't have pre-compiled modules for the default 2.6 kernel, so you'll have to manually compile the HostAP drivers.
apt-get install hostap-source
The TarBall will be downloaded to /usr/src/, which you will have to extract and compile. Once you have the hostap drivers installed, you will need to restart the pcmcia service so that it can load up new config files.
/etc/init.d/pcmcia stop ; /etc/init.d/pcmcia start
Once this is done, removing and re-inserting the card should now cause it to use the hostap driver instead of the orinoco driver, and you can configure wpasupplicant to use this new driver, as discussed on the WirelessNetworkSecurityNotes page.
Unfortunately the firmware on my card was too old to support WPA, but fortunately it is fairly easy to upgrade the firmware to a newer version that will.
This information came from Jun Sun's excellent 
prism flashing mini-howto. See that page for more details.
Step 1: install the flashing tool.
apt-get install hostap-utils
Step 2: get a newer firmware. There are different firmwares for chip revisions... check the table on his website for which firmware you need for your card.
wget http://linux.junsun.net/intersil-prism/firmware/1.8.4/sf010804.hex
Step 3: transfer the firmware onto the card
prism2_srec -v -f <interface name> sf010804.hex
The interface name is probably wlan0. I went from 1.4.3 to 1.8.4 with no problems. prism2_srec is smart enough to not do anything to the card if you have downloaded the wrong firmware. If you want to manually check first, run
prism2_srec <interface> sf010804.hex
and see if it gives any warnings about incompatibilities.
2 pages link to PrismWirelessChipset:
